System for checking a suspension of fluorescent material

ABSTRACT

The invention relates to a system for checking a suspension of solid particles, having a test tube for taking up and sedimentation of the suspension, having--an illuminating radiation source (L),--a test tube (P) is transparent to the illuminating radiation and the radiation emerging thereof, in which test medium is allowed to sediment and which can be located in the radiation path of the system,--optionally, a further test tube (PE), that is transparent to the illuminating radiation and the radiation emerging thereof, in which a reference or calibration liquid is allowed to sediment and which can be located in the radiation path of the system,--a sensor device to detect the illuminating radiation (S L )--a sensor device for detecting radiation emerging by transmission (S T ) from the test tube(s) (P E , P)--a sensor device for detecting the radiation (S F ) emerging from the test tube(s) at an angle other than 180°--a timer device (U) and--a computer (R) for processing the measured values obtained and outputting at least one output signal to the processing unit.

FIELD OF THE INVENTION

The invention relates to a system for checking a suspension of solidparticles, in a test tube for taking up the suspension and allowing itto sediment therein.

BACKGROUND OF THE INVENTION

Suspensions of solid particles in liquids are frequently used intechnical fields--for example, suspensions of barium sulphate in liquidas contrast medium for X-ray examination equipment, magnetizable,fluorescent particles in liquids for crack testing; lubricating oils,which as time goes on acquire an increased solid content of metallicfines, abrasive suspensions, etc.

Many of these suspensions are circulated in systems--for example, aslubricants or even the fluorescent fluid in crack testing equipment. Theability of the test equipment to make a statement depends, amongst otherthings, on these suspensions being intact--if there are too few solidparticles or if they have been damaged by mechanical stress, the testresults obtained with them are often poor or no longer usable. Theopposite case also exists where, for example, an increased input ofsolids into a liquid and therefore the formation of an ever increasinglyconcentrated suspension has to be checked, so that a statement can bemade regarding the continued suitability of the medium--for example, alubricating oil--in order to prevent damage to an engine. On the otherhand it is desirable, both from the environmental and cost points ofview, to use the suspension for as long as possible, in order to avoidunnecessary disposal.

Actually most engine oils and also most crack detecting agents arechanged after a pre-determined "service interval", as a preventivemeasure--although for many applications this should not be necessary. Onthe other hand increased stress on the suspension--for example, from theaction of particularly high shearing forces on the liquid and also whenworking at high temperature--the suspension may degrade more quickly orbe "used up".

Hitherto such suspensions, in the case of conductive materials, wereoften tested by way of conductivity tests (for retarding agents), pHvalue measurements or even by sedimentation and visual observationthereof in a so-called ASTM bulb. The conductivity test had thedisadvantage that even a slight change in the electrolyte or watercontent of oil, for example, led to completely incorrectmeasurements--the ASTM bulb had the serious drawback of up to nowdelivering values that were not automatically acquirable and couldtherefore only be measured subjectively.

From EP-A-O 427 996 discloses a process for measuring aromatichydrocarbons, where fluorescence spectroscopy is used to measure theconcentration of fluorescent, i.e. liquid-dissolved hydrocarbons. Inother words, in this case, clear liquids and not suspensions are beingmeasured.

DE-A-43 11 543 relates to a device for determining the concentration ofa test liquid, which only measures the luminescence, i.e. the lightemitted by the test liquid but not whether this lunescence may possiblychange in time and therefore does not permit any statement to be made asto whether the luminescence occurs as a result of abraded fluorescentmaterial or as a result of the particles themselves, to which thefluorescrible material is bound. This document also does not enable anymeasurements to be made of the solid density of the suspension, sincethe emission of fluorescent light does not enable any such statements tobe made.

JP-A-62-255851 in turn, relates to the measurement of the rate ofsedimentation of a material, as required for coagulation measuringdevices, for example for the solvent coagulation of plastics. In otherwords, the increase in size of the suspended particles is measured overtime. The area of the invention on the other hand, relates to themeasurement of fluorescent material, which over a period of time, alsodecreases in size.

OBJECTS AND SUMMARY OF THE INVENTION

Consequently, it is the object of the invention to provide a systemwhich automatically, reliably and verifiably checks the functionalperformance of suspension of solids in liquid.

The problem is solved according to the invention by a system forchecking a suspension of solid particles, in a test tube for taking upthe the suspension and allowing same to sediment therein with: anilluminating radiation source (L), a test tube (P) that is transparentto the illuminating radiation and the radiation emerging from the same,and which can be located in the radiation path, optionally, a furthertest tube (PE) that is transparent to the illuminating radiation and theradiation emerging from the same, in which a reference or calibrationliquid is allowed to sediment and which can be located in the radiationpath, a sensor device to detect the illuminating radiation (SL), asensor device for detecting radiation emerging by transmission (ST) fromthe test tube(s) (PE, P), a sensor device for detecting the radiation(SF) emerging from the test tube(s) at an angle other than 180°, a timerdevice (U) to initiate the recording of measured values, taken atintervals, thereof solid suspension introduced into the test tube andfor introducing new solid suspensions after pre-determined timeintervals; and a computer (R) for processing the measured valuesobtained and outputting at least one output signal to the processingunit. Any known illuminating devices, such as LASER or even UV lamps,normal lamps etc. may be used for this. For test tubes, round but alsosquare, cuvette-type containers, which allow problem-free transmissionand also satisfactory cleaning, can be considered.

Preferably the system is checking a suspension of fluorescent orphosphorescent material, having a source of excitation radiation withradiation within the fluorescence/phospho-rescence excitation wavelengthrange, a test tube (P) that is transparent to the illumination radiationand to the fluorescence and/or phosphorescence radiation emergingthereof, in which test medium is allowed to sediment and which can belocated in the radiation path of the system; optio-nally, a further testtube (PE) that is transparent to the illumination radiation and thefluorescence/phosphorescence radiation emerging thereof, in which areference or calibration liquid is allowed to sediment and which can belocated in the radiation path of the system; a sensor device fordetecting the illumination radiation (SL); a sensor device for detectingthe radiation emerging from the test tube(s) (PE, P) by transmission(ST); a sensor device for detecting fluorescence and/or phosphorescenceradiation (SF) emerging from the test tube(s); a timer device (U) whichenables measured values to be taken and duly stored after pre-determinedintervals; and also a computer (R) for processing the measured valuesobtained and outputting at least one output signal to the processingunit.

The system according to the invention is preferably arranged in such away that the test tube (P) is connected to the bypass of a system thatis continuously circulating suspension, i.e. constant--andautomatable--monitoring of the test medium and documentation of themonitoring values to satisfy documentation obligations are possible.

Preferably the fluorescent solid material of the test medium suspensionhas particles combined with fluorescent or phosporescible dye.

It may be beneficial if the wavelength of the illumination source hasonly a small band width, for example, by connecting a band filter inseries or by using a laser--this eliminates interference from other waveranges more reliably.

Particularly suitable as sensor devices for measuringfluorescence/phosphorescence (SF) are sensors protected by cut-off orband filters, which eliminate wavelengths at least in the area of theexcitation wavelengths.

Usually the computer (R) processes the measured values of thetransmission radiation and the radiation emerging from the test tube atan angle other than 180°, after predetermined time intervals, comparesthe values thus obtained with a stored rating table and produces atleast one corresponding output signal.

This minimum of one output signal from the computer (R) is output to adisplay unit (D), such as an acoustic sensor, a monitor, a pointerinstrument etc.

Preferably at least one output signal from the computer (R) is used tocontrol the renewal of a suspension, to supplement a suspension or toshut down the system working with the suspension.

At least one output signal will be preferably transmitted to a recordingunit to generate permanent records on storage media, such as print-outs,test documents or CD-ROM etc., which produce test documents about thequality of the fluorescent suspension under the recording conditions.

Preferably a recording device to make a permanent record of thesignal(s) produced, such as a printer etc., shall be connecteddownstream of the indicating display device (20) or any correspondingvisual display unit.

Because now for the first time a system is being proposed that isautomatable and even capable of operating continuously and whichtransmits information at regular intervals concerning the operationalcapability of the suspension, it is possible, for the first time, todocument the function of the suspension, for example, in the form oftest documents and, as a result, to meet claims for compensation or evento satisfy requirements imposed by ISO 9000.

Although the system is explained below with the help of fluorescentcrack detecting agents, it is taken for granted by the expert in thefield of optical testing methods, that the system can also be used,mutatis mutandis, to check other suspensions, where a correspondingevaluation program is then used. What is particularly important is theevaluation in time of the data, as this reflects the sedimentationbehaviour and the change with time.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail below with the help of anembodiment, namely a system for checking a fluorescent crack detectingagent and the accompanying drawing, but is in no way limited to this.

FIG. 1 shows a block diagram of an initial embodiment of a systemaccording to the invention;

FIG. 2 shows a block diagram of a further embodiment of a systemaccording to the invention;

FIG. 3 shows a schematic representation of an automatable test mediummeasuring unit; and

FIG. 4 shows the dependence of fluorescence and transmission of the testmedium, as measured by the unit shown in FIG. 4, upon time.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1 and FIG. 3, these are systems that are used asadditional equipment in a cost-control package and/or safetydocumentation as an addition to a crack detection system, in particularone that operates automatically, where the test tube P istransilluminated by a lamp L, acting as the source of radiation and theradiation passing through the test tube by transmission (ST) ismeasured, preferably at 180° to the direction of irradiation. A furthersensor SF is provided for radiation that does not emerge in thedirection of transmission, where this sensor SF measures either onlycertain wavelengths of the emerging light (by the connection of bandfilters upstream) or the total radiation, using measures that areactually known.

Both values measured by the sensors are transmitted together with atimer value (U) to the computer R, which then processes them into atleast one output signal, which can then be transmitted to printers ordisplay instruments and used as a control signal for remote systems etc.

FIG. 2 shows a more elaborate system, which makes it possiblesimultaneously to check a test medium in a calibration test tube. Knowncalibration liquid--for example unused test medium--or even a whitestandard etc., can be introduced into this calibration test tube, thusproviding a permanent measurement reference. The radiation source can beused, by known means (beam divider etc.), to illuminate both test tubesevenly--the same applies to the sensors.

In the embodiment in FIG. 2 the measurement is even more accuratebecause of the internal standard.

In systems where the devices according to the invention are preferablyused, workpieces are magnetized for the magnetic particle test by aknown method, they are sprayed with a test medium containing dyes, inparticular also ferromagnetic material having fluorescent dyes, such astest media containing iron or an iron compound, with concentration ofiron particles on surface flaws and said workpieces are observed underUV or visible light and the crack image thus obtained is compared withthe crack image on at least one check test body.

This provides regular checking of the circulating fluid markingmedium--which after dripping off the test specimen is regularlyrecovered in a collecting tank and re-used--for function, ageing, lossof magnetizable particles--because residual particles are usually leftbehind on the test specimens. The life of the medium and the accuracy ofthe technique for which it is used can now be drastically improved. Itis also recommended that the irradiation devices be regularly checkedfor their operational capability--it was discovered that the UV lamps,which were mostly used to generate fluorescence, have to be checked bothin respect of their spectrum, on account of lamp ageing etc., and alsoon account of deterioration in function of the lamp as a result ofsoiling, which can result in a distorted image--irrespective of thefunctions of cost control and/or warranty. Because the function of thechecking system and of its individual components can now also be carriedout automatically at pre-set intervals, the following advantages areprovided:

the test medium suspension only has to be replaced or a resupplyorganised once it is known that it is exhausted and no longer deliverssatisfactory test results.

The lamps must be constantly checked for their emission. This means thatany drop in UV intensity within the lamp spectrum, as is generallyknown, can be compensated for by appropriate measures--either the lampcan be replaced, its operating voltage adjusted or even the sensitivityof the sensors correspondingly re-calibrated, to compensate for thereduced fluorescence brought about by reduced radiation intensity and torecalibrate the statement of fluorescence intensity in relation to thespecific equipment.

Because an automated test medium device, referred to as an "automatedASTM bulb", is provided, it can be ensured that changes in the testmedium suspension, which consists of a liquid containing ferromagneticparticles suspended in it, preferably stained with a fluorescent dye, ascan be detected by abrasion or disintegration of the ferromagneticparticles where the liquid is circulated for a long period, by dye beingdeposited on the particles or even loss of magnetic particles, whichremain on the various test bodies measured, are detected and theappropriate action taken. Thus, either a new suspension can then beused, ferromagnetic particles be added to the suspension or at least newsuspension re-ordered.

The test medium, e.g. the fluorescent, yellowish-green concentrate ofthe applicant, which contains additives, is subject to a check afterpre-determined check intervals, for example, roughly every two hoursafter the start of processing, using a known bulb-shaped controlcontainer (known as an "ASTM bulb"), which is provided with a level markand in which, following a settling time of 60 minutes, the level of theprecipitation is measured according to the graduation lines, therebydetermining whether the test liquid can still be used or not or whetherfresh indicator (particles) have to be added to the fluid. The relevantvalues are known to the expert in the field (see in particular, FIG. 4).In other words, it is important in the case of a test system which runscontinuously for days or similar periods or which even operatesintermittently to generate at least one signal quickly and reliably,providing a continous and constantly available check and which indicateswhether the work can be continued with the current test agent or howmuch longer it will still be available for use or whether a new testagent should be supplied. Processing the test signals obtained from themeasuring devices, can lead to considerable savings in test media.

To measure the cost of the test medium material parameter, the testmedium is checked by measuring the optical density and the fluorescentbehaviour--preferably automatically, at regular intervals.

For this purpose, as can be seen from FIG. 4, a test medium suspension,consisting of a liquid carrier and ferromagnetic, fluorescent particlesis tapped from the test medium circuit of the test system, is introducedinto a test tube or cuvette and left to stand so as to leave a liquidthat is still and non-turbulent, suitable for testing. The density ofthis still liquid is then measured in transmission using the knownsensor and the fluorescence is simultaneously measured by a sensor setto the wave length of the fluorescence radiation (in this case in thegreen area, as the fluorescence occurs there). From the time ofintroducing test medium into the test tube, measured values are taken atvarious time intervals. In each case, an initial value for transmissionand fluorescence is measured after introducing the fluid test mediumsuspension into the test tube and at least one further value is measuredin each case for T and F at time T after introduction.

As the test medium ages, so too does the size of the particles and theirfluorescibility. This leads to measured values which are depictedschematically in FIG. 5. Thereafter, there is an increase in extinctionbecause of the increasing proportion of smaller, slowly sinkingparticles caused by abrasion and the fluorescence decreases because thefluorescent material, as a result of radiation, is subject tophotochemical and general ageing because of the mechanical stress on thesame, as well as to further stress.

Hence, the testing medium test unit can measure the following variableswith accuracy and these result in an output signal from the test mediumtest unit, indicating the suitability of the test medium--the ingress ofdirt in the test medium, for example, abrasion from workpieces etc.,manifests itself as falling transmission and decreasing fluorescence atthe start of measurement (To); the penetration of water is shown in theform of rising transmission at (To) and the removal of water is shown asincreased concentration of particles, i.e. falling transmission andincreasing fluorescence. Where particles are lost, the initialfluorescence (Fo) decreases and where fluorescent material is abraded,fluorescence is maintained in the remaining liquid, once the magneticparticles, which are heavier than water, have sedimentd--in other wordsthe liquid of used test medium fluoresces more intensely after settling,than when the test medium is working properly (FT).

It is preferred that the test tube is developed as a kind ofself-cleaning flow cuvette--in other words, on completion of themeasurement, new liquid flows through the test tube, thus cleaning it. Aseparate CIP unit (cleaning-in process) for test tubes, may also beprovided to release impurities which cannot be removed by the testmedium, such as burnt or polymerised organic compounds, which may clogthe test tube and thus lead to the distortion of measurements. Insteadof an indicator display unit or digital visual display unit (such as acounter or similar to display the output signals from the computer),these measurements can be transmitted to a print unit, e.g. a laserprinter or an ink-jet printer. The values that have been measured or areto be monitored are printed out as documents on a relevant recordingmaterial, such as writing paper, during the course of operation overseveral days, as well as over longer or even shorter operating periods.An appropriate timer (U) thus produces, for each time unit, a controldocument which in particular, allows subsequent checking of workpiececomponents or similar. In this case it is possible to correlate theindividual statistical values of the workpiece flow, such as type ornumber of part, number of units or other designation with the data fromone or more measured value units.

The test document also serves as information about a pre-set errorvariable interval as a function of time and about the type of workpiece.

The safety and control document also permits more reliable subsequentcontrol of operators working on VDUs, so that, for example, assessmentsof the marking element 20d in the colour fields, can be checked andoptionally, corrected.

Measurement of the data flow that goes back to brightness values canalso be beneficially carried out by a diode cell or other suitablemeans, as are known to the expert, instead of a camera. Thedocumentation can, of course, be generated remotely and stored by thedevice, by remote data transfer.

Although the invention has been explained on the basis of a preferredembodiment, the expert is familiar with modifications which fall underthe scope of protection of the claims. The invention is therefore, in noway limited to the form of embodiment described.

We claim:
 1. A system for checking a suspension of particles,comprisingan illuminating radiation source for emitting an illuminatingradiation; a test tube for receiving a suspension of particles, the testtube being situated in a radiation path of the illuminating radiationsource, the test tube being transparent to the illuminating radiationfrom the radiation source, the test tube being transparent to radiationemerging from the test tube; a first sensor for measuring radiationemerging from the test tube at a 180 degree angle relative to theradiation path; a second sensor for measuring radiation emerging fromthe test tube at a non-180 degree angle relative to the radiation path;a timer for initiating a recording of the measured values from the firstand second sensors at intervals; and a computer for processing themeasured values obtained and outputting at least one output signal. 2.The system according to claim 1, wherein the illuminating radiationsource emits radiation in the fluorescence/phosphorescence excitationwavelength range of the particles.
 3. The system according to claim 1,further comprisinga further test tube, the further test tube beingsituated in a second radiation path of the illuminating radiationsource, the further test tube being transparent to the illuminatingradiation from the radiation source, the further test tube beingtransparent to radiation emerging from the further test tube; andwhereinthe first sensor is for measuring radiation emerging from thetest tube and the further test tube at a 180 degree angle relative tothe respective radiation paths; and the second sensor is for measuringradiation emerging from the test tube and the further test tube at anon-180 degree angle relative to the respective radiation paths of theilluminating radiation source.
 4. The system according to claim 3,wherein the test tube contains a suspension of particles to beevaluated, and wherein the further test tube contains a referenceliquid.
 5. The system according to claim 4, wherein the computercompares the radiation emitted from the test tube measured by at leastone of the first and second sensors with the radiation emitted from thefurther test tube measured by at least one of the first and secondsensors.
 6. The system according to claim 2, further comprising a bandfilter disposed between the test tube and the second sensor, the bandfilter excluding a band of wavelengths, the band of wavelengthsincluding the excitation wavelengths.
 7. The system according to claim1, further comprisinga processing device including, a mechanism forcirculating the suspension of solid particles through the processingdevice; and whereinthe test tube being selectively coupled to themechanism to receive the suspension of particles.
 8. The systemaccording to claim 7, wherein, the computer is coupled to the processingdevice, the computer controlling the processing device to perform one ormore of a suspension renewal, a suspension supplementation, and a systemshut down.
 9. The system according to claim 1, wherein the computerprocesses the measured values received from the first and secondsensors, compares the measured values with a stored rating table, andoutputs a signal indicative of a result of the comparison.
 10. Thesystem according to claim 9, wherein the measured values from the firstand second sensors processed by the computer include values measured bythe first and second sensors just after introduction of the suspensioninto the test tube, and values measured by the first and second sensorsat a time T after introduction of the suspension into the test tube. 11.A system for checking a suspension of particles, comprisinganilluminating radiation source for emitting illuminating radiation; afirst sensor for measuring radiation, test tube for receiving asuspension of particles arranged in a radiation path of the radiationsource between the radiation source and the first sensor such that thefirst sensor measures radiation emerging from the test tube at a 180degree angle relative to the radiation path, the test tube beingtransparent to the illuminating radiation from the radiation source andto radiation emerging from the test tube; a second sensor for measuringradiation emerging from the test tube at a non-180 degree angle relativeto the radiation path; a timer for initiating timed recording of themeasured radiation from the first and second sensors; and a computercoupled to the timer for processing the measured radiation obtained fromthe first and second sensors and outputting at least one output signal.12. The system according to claim 11, wherein the radiation source emitsradiation in the fluorescence/phosphorescence excitation wavelengthrange of the particles.
 13. The system according to claim 11, furthercomprisingan additional test tube arranged in a second radiation path ofthe radiation source between the radiation source and the second sensor,the additional test tube being transparent to the illuminating radiationfrom the radiation source and to radiation emerging from the additionaltest tube; the first sensor being arranged to measure radiation emergingfrom the test tube and the additional test tube at a 180 degree anglerelative to the respective radiation paths; the second sensor beingarranged to measure radiation emerging from the test tube and theadditional test tube at a non-180 degree angle relative to therespective radiation paths.
 14. The system according to claim 13,wherein the test tube contains a suspension of particles to beevaluated, and wherein the additional test tube contains a referenceliquid.
 15. The system according to claim 14, wherein the computercompares the radiation emitted from the test tube measured by at leastone of the first and second sensors with the radiation emitted from theadditional test tube measured by at least one of the first and secondsensors.
 16. The system according to claim 14, wherein the referenceliquid includes a fluorescent solid material comprising fluorescent orphosphorescent dye.
 17. The system according to claim 12, furthercomprising a band filter disposed between the test tube and the secondsensor, the band filter excluding a band of wavelengths including theexcitation wavelengths.
 18. The system according to claim 11, furthercomprisinga processing device including a mechanism for continuouslycirculating the suspension of particles through the processing device,the test tube being selectively coupled to the mechanism to receive thesuspension of particles.
 19. The system according to claim 18, wherein,the computer is coupled to the processing device, the computercontrolling the processing device to perform one or more of a suspensionrenewal, a suspension supplementation, and a system shut down.
 20. Thesystem according to claim 11, wherein the computer processes themeasured radiation received from the first and second sensors, comparesthe measured radiation with a stored rating table, and outputs a signalindicative of a result of the comparison.
 21. The system according toclaim 20, wherein the measured radiation from the first and secondsensors processed by the computer include values measured by the firstand second sensors just after introduction of the suspension into thetest tube, and values measured by the first and second sensors at a timeT after introduction of the suspension into the test tube.
 22. Thesystem according to claim 11, wherein the radiation source has a smallband width.
 23. The system according to claim 11, wherein the at leastone output signal is transmitted to a recording unit to generatepermanent records on storage media to enable the production of testdocuments about the suspension of particles being checked.
 24. Thesystem according to claim 11, wherein the at least one output signal isoutput to a display unit.
 25. The system according to claim 24, whereinthe at least one output signal is directed to a recording deviceconnected to the display unit.